Move some test creation to its single user.

* subversion/tests/libsvn_wc/entries-compat.c
  (create_fake_wc): Move M subdir creation...
  (test_stubs): ... to this test, as no other test uses it.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1558616 13f79535-47bb-0310-9956-ffa450edef68